Telephone handsets for the hard-of-hearing are known, which comprise a variable gain amplifier which amplifies the sound uniformly in all the frequencies.
Special telephone earpieces for the hard-of-hearing are also known, provided with a hearing aid. These earpieces are coupled with a magnetic coil which transmits electromagnetic signals by induction to the hearing aid placed on the telephone position (T.).
The first of these known devices makes it possible to improve perception of the sounds by increasing the general sound level but it does not make any correction adapted to the individual deficiency of the user.
The second of these known devices makes it possible to telephone, using a hearing aid, but it makes no correction other than that due to the hearing aid.
The devices according to the invention have a different objective. In general, the ear of a person hard-of-hearing perceives with difficulty the sounds located in a determined frequency range.
A device according to the invention makes a spectral modification of the sounds intended to compensate the sensitivity curve of the ear by reinforcing the perception of the frequencies poorly perceived by the ear, with the result that, finally, the ear perceives all the frequencies with approximately the same sensitivity and the auditive acuteness of the user of an earpiece according to the invention is substantially uniform within the whole range of acoustic frequencies.